Cassette unit

ABSTRACT

A cassette unit for ionographic reproduction of images. The cassette has a first flat electrically conductive plate adapted to have an insulative surface associated therewith, a second flat electrically conductive plate, and a photoemissive surface associated with the second plate, the plates being spaced apart and the surfaces being spaced apart with the surfaces facing each other. The cassette includes means for connecting an electrical potential across the plates whereby when electromagnetic radiation is directed through the plates a latent electrostatic image can be ionographically formed on the insulative surface. Means is provided for maintaining a gas confined in the space between the surfaces.

United States Patent 1 1 11 1 3,930,156 Hindell Dec. 30, 1975 [54] CASSETTE UNIT FOREIGN PATENTS OR APPLICATIONS 1 lnvemorr Sidney Hindell, San Diego, Calif- 1,497,093 11/1962 Germany 250 315 [73] Assignee: Diagnostic Instruments, Inc., San

Diego, Calif. Primary Examiner-James W. Lawrence Filed: p 1974 Asslstant ExammerB. C. Anderson [21] Appl. NO.Z 458,809 ABSTRACT Related US. Application Data A cassette unit for ionographic reproduction of images. The cassette has a first flat electrically conductive plate adapted to have an insulative surface associated therewith, a second flat electrically conductive plate, and a photoemissive surface associated with the second plate, the plates being spaced apart and the surfaces being spaced apart with the surfaces facing each other. The cassette includes means for connecting an electrical potential across the plates whereby when electromagnetic radiation is directed through the plates a latent electrostatic image can be ionographically formed on the insulative surface. Means is provided for maintaining a gas confined in the space between the surfaces.

7 Claims, 9 Drawing Figures mung IFIG.7

Dec. 30, 1975 CASSETTE UNIT This is a continuation of application Ser. No. 264,247, filed June 19, 1972, now abandoned.

BACKGROUND OF THE INVENTION This invention is in the field of ionography. The general process known as ionography involves making X-ray images without the utilization of silver halide film. The basic process was disclosed by E. L. Criscuolo, in NAVORD Report 4033 of July 6, 1955, US. Pat. No. 2,900,515 of Aug. 18, 1959, to Criscuolo et al., in an article by R. A. Youshaw and J. AQl-lolloway in Nondestructive Testing, Vol. 17, September- October, page 297 (1959) and by K. H. Reiss in Z. Angew. Physik, Vol. 19, page 1 (1965). This process includes the utilization of two parallel plate electrodes. A d.c. voltage is applied across the gap between the electrodes such that one is a positive electrode or anode and the other is a negative electrode or cathode. When the positive electrode is nearest the X-ray beam, it must not absorb much of the X-ray beam. it has affixed to it an image receiving sheet which may be transparent or opaque but must be an electrical insulator such as a thin sheet of a plastic film or the like. The negative electrode has a thin film or layer of a material which is an efficient absorber of X-rays. In the aforementioned Reiss reference, a heavy metal such as lead was utilized as an absorber of the X-rays and was, in effect, a photoemitter. The image receiving insulator on the anode and the photoemissive layer on the cathode face each other across the gap between the electrodes with the object being examined disposed on either the outer side of the anode or the cathode, preferably on the outer side of the anode. A-quenching'gas is flowed or, in some cases, may be stationary in the gap between the electrodes. When an object disposed adjacent the anode is irradiated by X-rays or gamma rays, the electromagnetic radiation is differentially absorbed by the object and passes through the transmissive anode-and insulator layer affixed thereto and across the gap to strike the photoemitter. The radiation is strongly absorbed by the photoemitter which, as a consequence, ejects electrons having energies up to many kilo-electron volts. The number of electrons emitted is dependent upon the number of X-ray photons absorbed in that portion, the depth of the absorption, and the photon energy. On leaving the photoemitter surface, the electrons find themselves in the d.c. field between the electrodes and travel toward the positive electrode. The quenching gas serves to slow down the electrons so that they will not scatter when reaching the insulator and to increase their number by secondary ionization. Upon arriving at the insulator surface, the electrons, and any negative ions which may have been formed by attachment to. components of the quenching gas, are collected in an image configuration .forminga latent electrostatic image consisting of negative charges corresponding to elements or portions of the object which are relatively transparent to X-rays,.and no charges or fewer charges corresponding to portions or elements of the object which are opaque or relatively opaque to X-rays. This latent image is then made visible by development or by cathode ray tube display techniques.

One of the potential practicallimitations on commercial utilization of the aforegoing ionographic process is that it requires separate handling of the spaced-apart plates, disposition of the insulative substrate adjacent 2 one of the plates and, most importantly, maintaining the relatively critical gap between the plates. The handling of the separate components and their assembly prior to producing a latent electrostatic image, and disassembly thereof after the electrostatic image is produced so that development can take place, is a time-consuming process which can significantly impede the rapid production of successive images. Another disadvantage of the foregoing process from a practical commercial standpoint relates to the requirement of the quenching gas in the gap between the plates. Heretofore, theplates would have to be assembled in their relative positions and disposed in a chamher through which the quenching gas could pass, adding significant bulk to the apparatus.

SUMMARY OF THE INVENTION It is an object of this invention to provide a cassette unit wherein the plates in an ionographic process together with an insulative substrate can be prealigned and assembled into a compact readily usable unit.

Another object of this invention is to provide a cassette including the spaced-apart plates required for the process of ionography and wherein an insulative substrate having an electrostatic image produced thereon can be easily removed from the cassette unit prior to v the'development of an electrostatic image.

Still another object of this invention is to provide a cassette unitfor use in the production of an image from an ionographic process wherein a quenching gas can be readily maintained in a gap between the plates of the cassette.

The above and other objects of this invention are accomplished by a novel cassette unit for ionographic reproduction of images which is comprised of a first flat electrically conductive plate, an insulative surface associated with the first plate, a second flat electrically conductive plate, and a photosensitive surface associated with the second plate. The plates are spaced apart and the surfaces are spaced apart with the surfaces facing each other. A connector fitting is secured to at least one of the plates for connecting an alectrical potential, i.e., a relatively high d.c. voltage, across the plates whereby when electromagnetic radiation is directed through said plates a latent electrostatic image can be ionographically formed on the insulative surface. The connector fitting includes a gas port for admitting a gas between the surfaces. Means preferably constituted by a gas-tight envelope enclosing both plates is provided for maintaining the space between BRlEF DESCRlPTlON OF THE DRAWlNGS FIG. 1 is a perspective of a cassette unit of this invention;

FIG. 2 is an exploded cross section of the cassette;

FIG. 3 is a partially cross-sectioned plan view of a connector fitting of the cassette;

FIG. 4 is a perspective of aportion of the connector 1 fitting;

FIG. Sis a view taken along line 5-5 of FIG. 4 showing the opposite side of the connector fitting depicted in FIG. 4;

FIG. 6 is a partial cross section of the cassette showing the attachment of a first portion of the connector drawings.

- DESCRIPTION OF THE PREFERRED EMBODIMENTS Turning now to the drawings, there is seen in FIG. 1

anassembled cassette unit 11 of this invention. As seen, the cassette unit 11 is enclosed in an outer gastight envelope 13 having an exposed outer portion of a connector assembly 15 by means of which an electrical potential source and a gas source can be interconi nected with cassette unit 11.

Cassette unit 11 is a multilayered structure, the details of'which are particularly seen in FIG. 2. As seen,

an outer gas-tight envelope of a pliable, preferably heat-shrinkable polymer film material surrounds the "cassette and is sealed along an edge 17 as shown in FIG.

1. Thus, in FIG. 2, the film 13 is shown at both the top and bottom of a multilayered structure since it encloses the cassette. The film serves to form a substantially gas-tight envelope as will be further explained. Within the outer envelope 13 are the basic plates of the cassette which include a first plate 19 which can be formed I of an insulative material such as glass, bakelite or other material that provides a flat surface to which is secured "a thin conductive coating 21 of a suitable metal such as aluminum,- beryllium or films or foils of these. The conductive surface 21 on plate 19 can either serve as a cathode or an anode in the ionographic process, depending upon the polarity of the source of potential connected thereto. A metal tab 23 is provided on a side of plate or substrate 19, which tab serves as a means for "interconnecting one side of the potential source via one contact of a connector fitting, as will be further described, with conductive surface 21. Plate 19 with its conductive surface 21 is adapted to have an insulative surface associated therewith, as later appears.

Disposed opposite from plate 19 in spaced, parallel relationship thereto, is a second plate 25 of an electrically conductive material such as aluminum or the like, having a photoemissive layer 27 thereon which faces the conductive surface 21 of plate 19. The photoemissive surface 27 can be of lead, lead oxide or other suitable photoemissive material. Preferably, photoemissive layer 27 is bonded to conductor plate 25. This can be accomplished through a variety of techniques such as vapor deposition of the photoemissive layer on plate 25 or mechanically bonding the layer to the plate by means such as well-known electrically conductive adhesives. Thus the two plates 19 and 25 form the basic spaced-apart plates to which an electrical source is connected and a potential difference maintained in accordance with the ionographic process. The gap distance and the parallel relationship between the two plates are maintained by a spacer element 29 disposed between the plates and which extends around the periphery of each of the plates at the margins thereof. Spacer element 29 is of a nonconductive material which can be machined or formed so it has flat and parallel opposite surfaces 34 and 35. Thus spacer element 29 precisely maintains the gap distance between spaced conductive surface 21 and photoemissive surface 27. Thus, for example, spacer element 29 may comprise nylon, Teflon or similar polymers.

Adjacent conductive surface 21 of plate 23 and secured thereto is a thin layer 31 of a hold-down material which serves to removably affix to the conductive surface 21 a receptor substrate 33, on which the image is formed during the ionographic process. In the iono graphic process, an electrical potential is connected across the plates and electromagneticradiation is directed through a subject and thence through the plates to form a latent electrostaticimage on substrate 33. For example, the hold-down layer 31 may comprise a compliant vinyl material such as Blue Vinyl supplied by Tilley Manufacturing Co. of San Carlos, California.

, Vinyl hold-down materials are well known in the art and have good adherence properties. The vinyl holddown layer 31 is placed against conductive surface 21, completely covering it and adhering thereto. Next, the insulative substrate 33 (which can be a polymeric film, for example) is placed against the vinyl hold-down material and becomes affixed thereto by the action of the layer 31. It can thus be seen that the object of the vinyl hold-down layer 31 is to cause substrate 33 to lie flat against conductive surface 21. Other means can obviously be utilized in place of vinyl hold-down layer 31 to so secure substrate 33. Such means, however, should provide for easy removal of substrate 33 from plate 19 after the development of the latent electrostatic image. For example, one can wet conductive surface 21 with alcohol and then place substrate 33 directly thereagainst utilizing surface tension to secure the film in place. Film edge compression may also be used to affix the substrate 33 to the conductive surface 21 wherein the natural bow of substrate 31 isused in conjunction with narrow strips of preferably compliant material attached to conductive coating 21. The longitudinal edges of the film would be constricted by the compliant strips, forcing and retaining the bowed film flat against plate 19.

It is to be noted that electrically conductive plate 25 has two gas ports 37 and 38 which communicate with respective openings 39 and 40 on the photoemissive layer inwardly from the outer edge of the plate. The function of the gas ports will be further explained. However, it is important that openings 39 and 40 of the gas ports in the photoemissive surface are located inward from spacer element 29 and thus allow gas to be directed into the gap area created between plates 19 and 25, i.e., the space between surfaces 27 and 33. In order to assemble the cassette, substrate 33 may first be secured on plate 19 by hold-down layer 31. Spacer element 29 is bonded to plate 25 by a suitable adhesive and portion 41 of connector 15, which includes a front surface 42 and a rear surface 44, is then attached to lower plate 25.

Turning to FIGS. 36, it can be seen that connector portion 41 is secured to lower plate 25 by three screws 43 seated within recesses 45 formed in the front surface 42. Portion 41 of the connector has a lip 47 integrally formed thereon at the top of the rear surface 44 which is spatially disposed above plate 25 so as'to leave a channel 49 between the lip 47 and surface 27 in which is then positioned plate 19 with layer 31 and receptor substrate 33 secured therebetween. Lip 47 serves to 57. Contact 55 is formed as seen in FIG. so as to contact conductive surface 23 on upper plate 19, while the contact 57 in turn is directed downwardly so as to contact the side of the lower plate 25. Pins 53 serve as means for interconnecting contacts 55 and 57 with the respective sides of a suitable d.c. potential source so as to apply the potential across the flat, conductive plate surfaces 21 and 27. The outer surface 42 of connector portion 41 further contains two threaded spaced-apart holes 59 which enable an outer or second portion 61 of the connector to be connected thereto by screws 63. Before the outer portion 61 of connector 15 is conn'ected to the first portion 41 by two screws 63, envelope 13 is placed over the assembled unit with connector portion 41 attached to lower plate 25.

As indicated, the envelope can comprise a conventional heat-shrinkable polymer film completely enclosing the cassette except for preformed openings for pins 53, the two gas ports 51 and 52, and threaded holes 59 on the portion 41 of the connector assembly. Thus, the envelope 13 may be aligned relative to the assembled plates by slipping the pins 53 through the openings provided in the envelope. This would align the remaining holes therein with the ports 51 and threaded holes 59. Seam 17 may then be sealed. Next, the outer portion 61 of connector 15 would be connected to the first portion 41 by means of the aforementioned screws 63. This second portion 61 of the connector has a surface 64 which is thus clamped against the surface 42 of the other portion 41 of the fitting with an area of the envelope clamped between these two surfaces, providing a seal between them. Portion 41- is then inside the envelope and portion 61 outside the envelope. The film envelope 13 accordingly forms a gas-tight seal for maintaining the space between the insulative and photoemissive surfaces in gas-tight relationship for maintaining a quenching gas confined within the gap therebetween. The film envelope also advantageously serves to maintain proper adjustment between the plates by clamping them together in parallel relationship. Additionally, the film prevents bowing of the plates if the gas pressure within the gap changes due to a temperature variation, since there is a layer of gas between the film and the outer surface of the plates which tends to balance out temperature-induced pressure changes of the gas in the gap. Other means can be provided to achieve the desired seal for maintaining a quenching gas confined within the gap. For example, an O-ring can be seated within a groove about the periphery of the plates and suitable clamps can be used to maintain peripheral pressure against the O-ring.

The outer portion 61 of connector 15 has two apertures 67 which align with pins 53 of the inner portion 41 and allow the pins to extend therethrough as seen in FIG. '3. Extending from the outer surface 65 of portion 61 are two tubular extensions 69 and 70 which communicate with ports 71 and 72, respectively, extending inwardly from the rear surface 63, as seen most clearly in FIG. 8. Ports 71 and 72, in turn, align with ports 51 and 52 formed in first connector portion 41. Thus, as seen in FIG. 3, flexible tubes 73 can be fitted onto extensions 69 and 70 so that gas can be directed into the cassette unit through inlet tube 69, for example, and out through the outlet tube 70, as shown by arrows. The quenching gas, which may be argon, for example, may thus be flowed through the cassette during the production of the image.

Alternatively, the cassette may be filled with the quenching gas and sealed, the image then being formed in the stationary gas atmosphere thereby provided, without a continuous flow thereof. For example, as seen in FIG. 9, the tubular gas inlet extension 69 and outlet extension 70 may each be sealed with a membrane 75 which may be punctured by needles 77 of the hypodermic type and thereby permit quenching gas to be admitted at one inlet tube 69 and withdrawn from the other tube 70. The needles may then be removed with the membrane 75 providing a suitable self-sealing function. Thus the quenching gas may be admitted to the cassette long prior to the use thereof, e.g., during the assembly and manufacture thereof.

It may be noted that, since the quenching gas must be directed to the area between the photoemissive and insulative surfaces associated with plates 19 and 25, inlet port 51 through connector portion 41 is inclined (see FIG. 8) so as to communicate with passage 37 in plate 25. Passage 37 carries the gas past the peripheral spacer 29 so that it can fill the gap enclosed by the spacer. Prior to filling the cassette with quenching gas, the film envelope 13 is heatshrunk after attaching connector portion 61. The shrink action forces out substantially all the air except that in the gap.

Extending from the outer side 65 of connector portion 61 are two spaced-apart parallel fingers 79, each having at its distal end an inwardly directed tang or projection 81 which serve to grip a plug element 83 such as shown in FIG. 3 for connection of a source of electrical potential to the pins or conductors53. Fingers 79 thereby serve as a means for retaining a plug 83 in place relative to the cassette unit. Between the two parallel fingers 79 is preferably located a pin 85 which will be seated in a recess of plug 83 only if the plug is connected with proper polarity.

The foregoing description has so far been concerned with the provision of gas ports in the connector fitting so that gas can be either continuously flowed through the cassette or at least sealed therein after having been previously admitted to the cassette. No gas port is required if the quenching gas will not be admitted to the cassette after assembly. Instead, the cassette may be assembled and sealed in an atmosphere of the desired gas. Thus, for example, the elements can be so assembled in a glove box or the like having an argon atmosphere, the film envelope 13 being placed around the unit and sealed along seam 17 while the unit is in the desired gas atmosphere. The suitable outer portion of the connector is not then attached until the film is shrunk while the cassette remains in the glove box. The outer portion 66 is then affixed to the inner portion of the gap.

the connector fitting, the gas then being sealed within The cassette unit may be assembled in a glove box as described above, but the outer film envelope could be shrunk outside the box. A needle of hypodermic type may then be inserted through the membrane of the single gas port to allow excess gas to exit from the unit when the film envelope is shrunk and the internal volume of the envelope thus decreased. Other quenchinggas filling schemes may, of course, be employed.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is' claimed is: A cassette for ionographic reproduction of images comprising:

" a first plate including a first flat electrode carrying a thin sheet of dielectric material smoothly adhered thereto but conveniently'peelable therefrom, one surface of said sheet being exposed and adapted to have formed thereon a latent electrostatic image; a second plate including a second fiat electrode having a photoemissive surface, said plates being spaced apart I with said surfaces opposing each other; I an electrically nonconductive spacer disposed between the plates to extend around the periphery of the plates at the margins thereof thereby to define a uniform gaseous filled gap between said opposing 4 surfaces; a connector having a first terminal in electrical I contact with the first electrode and a second terminal in electrical contact with the second electrode 'and adapted to be quick-detachably connected to v an electrical potential source; and quick-releasable means for maintaining said plates and spacer in an assembled relationship but which when released permits them freely and completely to separate, said quick-release means comprising a 1 surrounding packaging envelope of a pliable synthetic resin film material which is conveniently severable.

2. A cassette as set forth in claim 1 wherein the packaging envelope comprises a gas-tight envelope of heatshrinkable polymeric film material shrunk so as to firmly maintain the plates and spacer in their assembled relationship.

' 3. A cassette as set forth in claim 1 in which said connector includes means for admitting gas to the gap between said opposing surfaces and is adapted for quick interconnection with an external gas supply.

4. A cassette as set forth in claim 3 wherein said connector is disposed peripherally adjacent said plates and includes an inlet gas port and an outlet gas port each communicating with the gap between said opposing surfaces. i

5. A cassette as set forth in claim 1 in which said connector has a first portion secured to one of said plates and a second portion removably secured to said first portion with an area of said envelope being clamped between said portions, said first portion being inside said envelope and said second portion being outside said envelope.

6. A cassette for ionographic reproduction of images comprising:

a first plate including a first flat electrode which has secured to one face thereof a smooth flat continuous layer of a synthetic resin material having the property of maintaining a sheet of dielectric material smoothly facially adhered thereto but conveniently peelable therefrom, a sheet of dielectric material so removably adhered to the layer, one surface of said sheet being exposed and adapted to have formed thereon a latent electrostatic image;

a second plate including a second flat electrode having a photoemissive surface, said plates being spaced apart with said surfaces opposing each other;

an electrically nonconductive spacer disposed between the plates to extend around the periphery of the plates at the margins thereof thereby to define a uniform gaseous filled gap between said opposing surfaces;

a connector having a first terminal in electrical contact with the first electrode and a second terminal in electrical contact with the second electrode and adapted to be quick-detachably connectecd to an electrical potential source; and

quick-releasable means for maintaining said plates and spacer in an assembled relationship but which when released permits them freely and completely to separate said quick-release means comprising a surrounding packaging envelope of a pliable synthetic resin film material which is conveniently severable.

7.v A cassette as set forth in claim 6 wherein said synthetic resin material layer is a compliant vinyl resin layer.

. F I! II k 

1. A cassette for ionographic reproduction of images comprising: a first plate including a first flat electrode carrying a thin sheet of dielectric material smoothly adhered thereto but conveniently peelable therefrom, one surface of said sheet being exposed and adapted to have formed thereon a latent electrostatic image; a second plate including a second flat electrode having a photoemissive surface, said plates being spaced apart with said surfaces opposing each other; an electricalLy nonconductive spacer disposed between the plates to extend around the periphery of the plates at the margins thereof thereby to define a uniform gaseous filled gap between said opposing surfaces; a connector having a first terminal in electrical contact with the first electrode and a second terminal in electrical contact with the second electrode and adapted to be quick-detachably connected to an electrical potential source; and quick-releasable means for maintaining said plates and spacer in an assembled relationship but which when released permits them freely and completely to separate, said quick-release means comprising a surrounding packaging envelope of a pliable synthetic resin film material which is conveniently severable.
 2. A cassette as set forth in claim 1 wherein the packaging envelope comprises a gas-tight envelope of heat-shrinkable polymeric film material shrunk so as to firmly maintain the plates and spacer in their assembled relationship.
 3. A cassette as set forth in claim 1 in which said connector includes means for admitting gas to the gap between said opposing surfaces and is adapted for quick interconnection with an external gas supply.
 4. A cassette as set forth in claim 3 wherein said connector is disposed peripherally adjacent said plates and includes an inlet gas port and an outlet gas port each communicating with the gap between said opposing surfaces.
 5. A cassette as set forth in claim 1 in which said connector has a first portion secured to one of said plates and a second portion removably secured to said first portion with an area of said envelope being clamped between said portions, said first portion being inside said envelope and said second portion being outside said envelope.
 6. A cassette for ionographic reproduction of images comprising: a first plate including a first flat electrode which has secured to one face thereof a smooth flat continuous layer of a synthetic resin material having the property of maintaining a sheet of dielectric material smoothly facially adhered thereto but conveniently peelable therefrom, a sheet of dielectric material so removably adhered to the layer, one surface of said sheet being exposed and adapted to have formed thereon a latent electrostatic image; a second plate including a second flat electrode having a photoemissive surface, said plates being spaced apart with said surfaces opposing each other; an electrically nonconductive spacer disposed between the plates to extend around the periphery of the plates at the margins thereof thereby to define a uniform gaseous filled gap between said opposing surfaces; a connector having a first terminal in electrical contact with the first electrode and a second terminal in electrical contact with the second electrode and adapted to be quick-detachably connectecd to an electrical potential source; and quick-releasable means for maintaining said plates and spacer in an assembled relationship but which when released permits them freely and completely to separate said quick-release means comprising a surrounding packaging envelope of a pliable synthetic resin film material which is conveniently severable.
 7. A cassette as set forth in claim 6 wherein said synthetic resin material layer is a compliant vinyl resin layer. 